When encoding an audio signal, to secure a short latency time, the length of a frame, which is a basic unit of encoding, should be small. Alternatively, to secure high sound quality, the length of a frame should be enough long to achieve a sufficient frequency resolution. Thus, it is difficult to simultaneously obtain a short latency time and high sound quality.
General audio encoding systems may degrade quality of sound by reducing the length of a frame according to an application to be used in order to shorten a latency time. Alternatively, in order to shorten a latency time, general audio encoding systems may use a certain type of window function which precludes perfect reconstruction of sound. Particularly in applications that require a short latency time, a short frame causes a reduction in frequency resolution and sound quality.
In audio encoding systems which use a short window for a short latency time, a pitch filter may be used to reduce coding distortion that noticeably occurs on music and speech which have periodic waveforms.